Are we alone in the universe?

It’s one of the biggest and most complex questions out there: are we alone in the universe? The field of astrobiology studies the origin, viability and future of life on other planets, and asks, is planet earth really as unique as we think? Caleb Scharf, Director of Astrobiology at Columbia University joins Hari Sreenivasan to discuss these questions.


It's one of the biggest and most complex questions out there -- Are we alone in the universe?

The field of astrobiology studies the origin, viability, and future of life on other planets, and asks, is planet Earth really as unique as we think?

Joining me now is Caleb Scharf, Director of Astrobiology at Columbia University.

I'm sure you have the answer to this question -- Are we alone? -- right, but this is kind of a question that we've always wondered as soon as we had the capacity to wonder, and then when we were able to look at that beautiful image of the blue planet for the first time, and then we started looking around and seeing a kajillion of these, how many other blue ones are there?

How do we tackle that?

It's a great question, and I should say, we don't know whether there's anything else out there, which is a fascinating puzzle because, as you mention, we're at this point in our history where we've now discovered that there are other worlds around other stars, and 20 years ago, we didn't know if that was the case, and we suspected that there were probably planets around other stars, but we didn't know if it happened very often.

We now know that it happens very often -- essentially, every star that you see in the sky has a planetary system around it, and something like at least 15% of those planetary systems have worlds that could be other blue marbles like the famous picture that you're evoking.

And so the big question now is, do any of them harbor life?

And that's a big focus for science right now, but it is, also, this fundamental ancient question that we've asked for a very long time.

We have this kind of Goldilocks just far enough away from the sun, not too far.

There's so many things that had to go just right for the preconditions of life here.

What's to say 4 billion years ago that combination didn't repeat, considering that there's a kajillion different planets in the galaxies and solar systems?

Again, it's a great question, and it's really at the forefront of inquiry at the moment is how robust is this phenomenon that we call life.

What does it take to get it going and what does it take to sustain it across 4 billion years?

We tend to forget that we, or life on earth has been here for something like 4 billion years, and it's gone through many changes, and it's gone through many different environmental conditions.

So, on the one hand, it looks like life is pretty robust.

On the other hand, we still don't know what the key pieces are for the origin of life or the sustaining of life over timescales like that.

So it's still a central puzzle.

What are the factors that point to the possibility of this happening?

Is it just the sheer number of it -- I mean, the mathematical probability of one in a billion not so much if you have 50 billion?

That's right.

Well, that is our intuition.


And it may well turn out to be absolutely correct.

Scattered amongst the stars we see in the sky, there's lots of other life, but the truth is, we simply don't know, and it's very interesting because it's to do with the way in which we make inferences on the basis of very little data.

So I like to say that astrobiology is a field that has one datapoint, which is us.


And we can extrapolate from that, but it turns out to be really difficult.

You can't do much with one datapoint, and so we're in this kind of interesting point of tension where everything is saying surely there's got to be life out there, there has to be other life, and it may be abundant, but we still don't quite know.

We haven't crossed that next threshold.

Given the tools that we have today, how does science study the viability of life elsewhere?

I mean, we have one or two really great telescopes up in the sky, but, you know, there's lots of interpolation that has to happen based on how light is traveling to us, what sorts of gases that we see, and then, really, just to try to get down to that miniscule level and say, 'Is that planet viable?'


So with our telescopes, we're trying to probe the chemistry of distant planets, and, again, that's very difficult, and it's right at the forefront of current inquiry, and in the future, we're aiming to do better than just look for oxygen.

We're aiming to look at a whole host of different chemicals that might exist in a planetary atmosphere, for example, that give away the presence of a biosphere.

Now, of course, the really interesting thing would be if we get some of that data, and we say, 'Hey, this planet has oxygen.

Maybe it's got methane in the atmosphere.'

What do we do next?

How do we convince ourselves that there's life there?

That, I think, is a puzzle we've yet to tackle.

Even if, best-case scenario, we say it looks like there are signs of life on some distant planet, one, we're not necessarily -- we don't have the technology yet to be able to travel anywhere close to that 'cause a telescope might be able to see light-years out, right, but we're never gonna be able to travel that, and then, two, life there might not have evolved the same way that life here evolved.

There's so many wonderful puzzles in this field.

We look at our surroundings and go, 'Wow.

This is just perfect for us.'


But in truth, we came out of those circumstances, and so it's only natural that they will seem to work well for us.

But this question of could it have happened differently, and you'd still, after 4 billion years, arrive at thinking, supposedly intelligent organisms like us.

Also, something we want to try to understand much, much better, because it's deeply linked to questions of chance and chaos in the universe.

It's linked to fundamentals of evolution.

How does evolution work on these very long timescales?

What are other possible trajectories that you can take and still end up at roughly the same place?

So, the marvelous thing about astrobiology as a science is, although you're asking questions about life elsewhere in the universe, ultimately it comes back to answer our deepest questions about ourselves, I think.

Got a very cool job -- Director of Astrobiology at Columbia University -- Caleb Scharf.

Thanks for joining us.

My pleasure.